Particle filters may be used for engines with compression ignition and applied ignition. Once a certain quantity of fine dust, for example in the form of soot and/or unburned hydrocarbons, has collected in the particle filter, removal may be desired (regeneration of the particle filter), in order to minimize a likelihood of degrading the particle filter and to decrease backpressure.
One method for regenerating the particulate filter uses nitrogen dioxide (NO2) contained in the exhaust gas for continuous oxidation of the soot to form carbon dioxide (CO2) and nitrogen monoxide (NO). This method demands sufficiently high temperatures and NO2 concentrations which may be achieved only in full-load operation of the combustion engine, for example in freeway driving. In partial-load operation, on the other hand, for example in urban driving, this method may be executed during only some driving conditions, which may decrease particulate filter longevity. These shortcomings may be further exasperated due to unpredictable driving (e.g., driving short distances, long distances, on hilly terrain, on freeways, etc.) which may not lead to full-load operation, resulting in passive regeneration conditions not being met.
In addition, government agencies may demand the reduction of NOx emissions, so that NO2 is removed from the exhaust gas flow after leaving the combustion engine, and consequently is no longer available for particle filter regeneration.
Another method of particle filter regeneration may utilize increasing the exhaust gas temperature, so that a regeneration temperature may be met. Additional fuel may be used to increase the exhaust gas temperature, resulting in an active regeneration. This can be delivered via a post-injection into the combustion chamber of the combustion engine or into the exhaust gas flow downstream of the combustion engine.
Regeneration of the particle filter may be accompanied by further measures such as a restrictor along the air path (flow path of the exhaust gas flow), for example, and may be desired after several hundred kilometers. The measures described may also be combined with one another.
A regeneration condition of the particle filter temperatures may include a regeneration temperature equal to approximately 600° C. present for a threshold duration of time (e.g., minutes). Introduction of additives may decrease the regeneration temperature to 450° C. These temperatures can only be achieved if certain operating parameters demanded of the combustion engine are fulfilled, for example the period of operation and the speed of a vehicle powered by the combustion engine.
If the combustion engine is run only for short periods, on the other hand, possibly with prolonged intervening pauses, then regeneration temperatures may not be reached and the particle filter cannot be successfully regenerated, so that more and more soot accumulates in the particle filter. As a result, for example, the driver of a vehicle having such a combustion engine, may be called upon, for example by means of a corresponding display on the instrument panel, to run the combustion engine in full-load operation, for example by using the freeway for a certain length of time, or to find a workshop or a dealer, in order to have a regeneration performed on the particle filter and to prevent clogging and degradation of the particle filter.
Certain bacteria or fungi in seaweed are also known to decompose carbon-laden impurities, for example crude oil, (Bik H M, Halanych K M, Sharma J, Thomas W K (2012) Dramatic Shifts in Benthic Microbial Eukaryote Communities following the Deepwater Horizon Oil Spill. PLoS ONE 7(6): e38550. https://doi.org/10.1371/journal.pone.0038550).
The bacteria may be termed hydrocarbonoclastic bacteria (HCBs). They occur naturally but due to a lack of nutrients are generally only found in very low concentrations.
The present disclosure describes a possible way of reducing or eliminating the problems described and the resulting benefits. In one examples, the problems may be at least partially solved by certain micro-organisms, which are capable of breaking down carbon-laden constituents contained in the soot, able to remove soot from the particle filter at low temperatures. The inventors have recognized that the naturally occurring micro-organisms such as HCBs, for example, which are capable of breaking down carbon-laden contaminants, encounter optimum living conditions in or on a particle filter, since the filtered soot constitutes a source of carbon and hydrocarbons; oxygen is present in the ambient air, and a desired quantity of water is also available, which is produced by the combustion process in the combustion engine and condensation once the combustion engine has been switched off.
The regeneration process here is a slow process compared to the methods described in the previous example and is also capable of running, for example, whilst the combustion engine is switched off and not in an operating state, for example whilst a motor vehicle according to the disclosure is parked.
A method according to the disclosure is therefore also suitable for regenerating the particle filter for combustion engines in partial-load operation, for example in motor vehicles which are used predominantly for short distances. A desire to deliver additional fuel or fuel additives can be reduced or even entirely eliminated.
A particle filter according to the disclosure for removing carbon-laden soot from the exhaust gas flow of a combustion engine comprises micro-organisms that break down constituents, in particular carbon-laden constituents, contained in the soot.
For example, the micro-organisms may be disposed on, next to and/or in the particle filter. The particle filter may take the form of a wall-flow filter, in which the exhaust gas flow flows through a porous wall in the particle filter. The porous wall may be built up from fibers and/or powders, which may comprise ceramics and/or metals.
Conditions for breaking down constituents contained in the soot may be relatively severe, wherein temperatures may fluctuate from low to high. Thus, it may be desired of a micro-organism configured to break down the soot to be able to withstand large temperature changes. One example of such a micro-organism may include hydrocarbonoclastic bacteria, fungi, and/or archaea, as they have a high tolerance to variations in temperature.
In some embodiments, an arrangement of the present disclosure comprises a combustion engine producing an exhaust gas flow, and an exhaust system connected to the combustion engine for receiving the exhaust gas flow, having a particle filter as exhaust gas aftertreatment device. In some embodiments, the particle filter may take the form of a diesel particle filter or an SCR-coated particle filter, that is to say a particle filter which also serves for selective catalytic reduction.
The arrangement may further comprise devices for regenerating the particle filter. More specifically, the arrangement may further comprise device for regenerating the particle filter during conditions where regeneration via the micro-organisms proceeds too slowly, for example, because the operating characteristics of the combustion engine cause more fine dust to accumulate in the particle filter than can be broken down. During such engine conditions, other measures can be taken to regenerate the particle filter, such as the arrangement of an exothermic catalytic converter, for example, which generates heat from unburned fuel by an exothermic reaction, upstream of the particle filter, or the delivery of additional fuel, as described above.
In some embodiments, the exhaust system may further comprise a feed device for delivering a composition having the micro-organisms that break down constituents contained in the fine dust to the exhaust gas flow and/or directly to the particle filter. In some examples, the micro-organisms are hydrocarbonoclastic micro-organisms.
In some examples, the feed device may be arranged upstream of the particle filter to deliver the micro-organisms to the exhaust gas flow upstream of the particle filter. Delivering the micro-organisms to the exhaust gas flow allows the composition to flow to the particle filter together with exhaust gas. The feed device may be an injector.
The composition, for example, may be an aqueous composition, such as an aqueous suspension of the micro-organisms, for example. The composition may optionally comprise one or more additives for exhaust gas aftertreatment, for example an ammonia-forming additive such as a urea solution for treatment of the exhaust gas flow in an SCR catalytic converter.
The feed device may comprise a controllable valve and/or a controllable pump device, so as to be able to control or regulate the quantity of the composition to be delivered. Control or regulation may be undertaken, for example, as a function of prevailing pressures and/or temperatures.
The feed device enables the micro-organisms to be delivered to the particle filter. Depending on conditions, for example as a function of the prevailing temperatures, a delivery of the micro-organisms may be desired more or less often, in order to counteract a reduction in the number of micro-organisms and to maintain the regeneration of the particle filter via the micro-organisms.
In some embodiments, the exhaust system may comprise a reservoir for the composition comprising the micro-organisms coupled to the feed device. A hose or similar device may fluidly couple the reservoir to the feed device.
The reservoir, for example, may be an existing reservoir for an exhaust gas aftertreatment additive, for example a tank for a urea solution. Thus, the micro-organism may be mixed with the urea solution.
In some embodiments, the exhaust system may comprise at least one further exhaust gas aftertreatment device. The feed device may be shaped to deliver the composition to the exhaust gas flow upstream or downstream of the further exhaust gas aftertreatment device. In some examples, more than one feed device may be arranged in an exhaust passage such that a first feed device may deliver the composition to the exhaust gas flow upstream of the further exhaust gas aftertreatment device and a second feed device may deliver the composition downstream of the further exhaust gas aftertreatment device. The further exhaust gas aftertreatment device may be upstream of the exhaust gas aftertreatment device.
The further exhaust gas aftertreatment device, for example, may be an oxidation catalytic converter, for example a diesel oxidation catalytic converter, a nitrogen oxide storage catalytic converter, or an SCR catalytic converter.
In order to prevent the further exhaust gas aftertreatment device impairing the regeneration effect of the micro-organisms, it may be desired to deliver the composition having the micro-organisms to the exhaust gas flow only downstream of the further exhaust gas aftertreatment device.
If the further exhaust gas aftertreatment device is an SCR catalytic converter, for example, delivery upstream of the SCR catalytic converter may be desired. This allows delivery in conjunction with the ammonia-forming additive needed by the SCR catalytic converter, obviating the desire for a further feed device and a further reservoir.
In some embodiments, the arrangement may comprise a control unit, which is designed to control the feed device as a function of the temperature, for example the temperature of the particle filter or the temperature of the exhaust gas flow upstream of the particle filter, and/or of the pressure, for example the pressure of the exhaust gas flow upstream of the particle filter, and/or as a function of an operating state of the combustion engine, for example as a function of whether the combustion engine is in an on or off state, and/or the time which has elapsed since a specific event, for example switching-off of the combustion engine, or the time remaining until a specific event.
The temperature may be determined via feedback from a temperature sensor, and the pressures via feedback from a pressure sensor. The control unit allows delivery of the composition to be controlled according to one or more of temperature and pressure. If it is estimated, for example, that the particle filter comprises an insufficient number of micro-organisms for regenerating the particle filter, a larger quantity of the composition may be delivered. The delivery may furthermore be purposely increased if regeneration conditions of the particle filter by the micro-organisms may be such that a regeneration rate may be increased. This may be the case, for example, after switching off the combustion engine, since then the temperature of the exhaust gas flow and hence also the temperature of the particle filter fall, so that thermal degradation of the micro-organisms is reduced.
Further embodiments of the exhaust system may furthermore comprise a tailpipe and where the particle filter may be arranged in the area of the tailpipe.
Towards the outlet of the exhaust system, that is to say with increasing distance from the combustion engine, the temperature of the exhaust gas flow may diminish. Since in contrast to the existing methods for regenerating the particle filter, the regeneration according to the disclosure by means of micro-organisms may not desire high temperatures, the micro-organisms instead being capable, for example, of regenerating the particle filter even at ambient temperature, the particle filter according to the disclosure can also be arranged proximally to the tailpipe outside of a close-coupled position where exhaust gas temperatures and pressures are lower.
This moreover has the effect, as the temperature falls, of also reducing the volumetric flow and hence the backpressure, so that the complications due to the backpressure, as initially described, can be reduced or even prevented.
Furthermore, arranging the particle filter in the area of the tailpipe creates more overall space for the arrangement of further exhaust gas aftertreatment devices in proximity to the combustion engine. This may be desired for exhaust gas aftertreatment devices which are adequately efficient only at high temperatures, for example catalytic converters which desire a rapid rise to their light-off temperature to reduce the pollutant emissions sufficiently.
A motor vehicle according to the disclosure comprises one of the arrangements previously described. The term “motor vehicle” is taken to mean a vehicle powered by an engine, for example a land vehicle, an aircraft or a watercraft.
A method according to the disclosure for regenerating a particle filter arranged in an exhaust gas flow from a combustion engine, for example the combustion engine of a motor vehicle, as exhaust gas aftertreatment device comprises bringing the particle filter into contact with micro-organisms that break down constituents contained in the fine dust.
They may be brought into contact, for example, by disposing the micro-organisms on, next to or in the particle filter, so that constituents, in particular carbon-laden constituents, contained in the filtered fine dust can be broken down.
In some examples, the micro-organisms that break down constituents contained in the fine dust may be selected from a group comprising hydrocarbonoclastic bacteria, fungi, and archaea.
Thus, in one example, the problems described above may be at least partially solved by a method for regenerating a particle filter via a micro-organism that breaks down carbon-containing compounds during a first condition. The first condition may include where an engine is deactivated, wherein fuel delivery to the deactivated engine is prevented.
In some examples, the method further comprises a delivery of a composition having the micro-organisms that break constituents contained in the fine dust to the exhaust gas flow, for example upstream of the particle filter, and/or directly to the particle filter.
In some examples, the composition may be delivered together with an additive for an SCR catalytic converter. The additive may be an ammonia-forming composition, for example a urea solution.
In some examples, delivery of the composition may be initiated by switching off the combustion engine, followed by a significant reduction of a temperature or a pressure or by the elapsing of a period of time.
In other words, delivery may be performed as a function of one of said initiating events. This can allow a delivery of the composition tailored to the need, for example matched to the operation of the combustion engine.
Initiating delivery of the composition by switching off the combustion engine serves to ensure that a fresh population of micro-organisms is fed to the particle filter, which may regenerate the filter during an operating state when the combustion engine is switched off, for example during a motor vehicle parking operation. A more rapid regeneration of the particle filter can thereby be achieved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.